The plano-convex lenses from LBTEK feature one convex surface and one flat surface, providing positive focal lengths typically used for beam reduction, focal length shortening, or imaging magnification applications. To minimize spherical aberration, when a plano-convex lens is used for focusing a collimated beam, the beam should be incident on the curved surface; when collimating a point source, the beam should be incident on the flat surface. ZnSe plano-convex lenses from LBTEK are coated with 4.5–7.5 μm AR coating on both surface to reduce the reflectivity of the lens. ZnSe is selected for its high transmittance across mid-to-far infrared spectra, with a refractive index of approximately 2.89 in the 0.5–15 μm range. Its low absorption at 10.6 μm makes it the preferred material for high-power CO₂ laser optics, while its broad transmission band also enables widespread use in various optical systems. Note that ZnSe is toxic, wearing gloves when handling and wash hands after use. All lenses undergo precision machining and strict quality control, ensuring LBTEK delivers high-quality optical products at competitive prices.